Explosive full-field strain and crack dynamic fracture characteristics of a linear shaped charge

This study explores the full-field strain and dynamic fracture characteristics of a linear shaped charge under different initiation positions. The explosion dynamic caustic line experiment system is employed to examine the characteristics of the blast crack propagation of the linear shaped charge at different initiation positions and capture the dynamic information of the crack tip propagation speed and stress intensity factor. Furthermore, the digital image correlation method was used to show the strain evolution law of the linear shaped charge at different initiation positions, as well as the medium strain response of the charge near the explosion zone caused due to detonation transmission. The results show that in end-initiation, the wing crack length at the initiation point is the smallest, and the wing crack propagation length increases with the detonation propagation of the explosive. Conversely, in center-initiation, the propagation length of the wing cracks at the center is less than those at both ends. The propagation length of the wing cracks in the noninitiation end is the longest for end-initiation, where the velocities of the wing crack initiation and propagation are minimum. For center-initiation, the wing crack initiation and propagation velocities are the smallest, i.e., irrespective of the initiation position, the wing crack initiation and propagation velocities at the initiation point are lower than that at other locations. Based on the dynamic stress intensity factor analysis, irrespective of the initiation position, the center wing cracks are type Ⅰ cracks with the largest crack toughness, the stress intensity factor value is the maximum, and the wing cracks at the ends are type Ⅰ−Ⅱ composite cracks dominated by type Ⅱ. Based on the full-field strain analysis of the linear shaped charge, at end-initiation, the range of tension and strain action is mainly along the direction of explosive transmission, and the tension and strain action area at the noninitiation end is larger than that at the initiation end. The corresponding position of the maximum compressive strain is 0.67–0.83 times the charge length from the initiation point. When the center detonates, the action process of tension and compression strain propagates symmetrically from the center to both ends of the initiation, and the strain at the center is the largest. The compressive stress concentration at the end occurs under both initiation modes because the explosive transmission is the process of energy accumulation; thus, the effect of the explosive explosion on the medium grows increasingly stronger along the direction of explosive transmission.